1. Field of the Invention
This invention relates generally to semiconductor integrated circuit packages, and more particularly to a flex tape ball grid array package.
2. Description of the Related Art
Tape ball grid array packages (TBGA's) are an increasingly common form of packaging for integrated circuits. TBGA's comprise a flexible plastic tape comprising a dielectric material, such as Kapton, and a metal pattern (traces) formed on the dielectric material. The metal pattern is connected to bond pads on an integrated circuit by a tape automated bonding process or some other process, such as wire bonding as is shown in co-pending application Ser. No. 08/837,686, filed Apr. 21, 1997. Each of the traces is connected to a solder ball, which serves as the electrical interface between the package and a printed circuit board. In this manner, integrated circuit bond pads in TBGA's are electrically coupled to an appropriate solder ball.
The flexible tape material is relatively thin and therefore allows the entire package to be correspondingly thin and lightweight. These characteristics are beneficial for systems that are portable, such as cellular phones and other handheld electronic devices.
The metal pattern mentioned above is typically constructed by laminating a metal foil layer to the tape material or by evaporating metal on the tape material. The metal pattern is then formed by selectively etching away the metal layer. The number of traces that may be created in this fashion for a given area of tape (i.e. the density of traces) is limited by etch techniques. It would be desirable to increase the trace density of conventional TBGS'S.